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Spores
In biology, a spore is a unit of sexual (in fungi) or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, fungi and protozoa. They were thought to have appeared as early as the mid-late Ordovician period as an adaptation of early land plants. Bacterial spores are not part of a sexual cycle, but are resistant structures used for survival under unfavourable conditions. Myxozoan spores release amoeboid infectious germs ("amoebulae") into their hosts for parasitic infection, but also reproduce within the hosts through the pairing of two nuclei within the plasmodium, which develops from the amoebula. In plants, spores are usually haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte. In some rare cases, a diploid spore is also produced in some algae, or fungi. Under favourable conditions, the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacterial Spore
An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form (''endo'' means 'within'), but it is not a true spore (i.e., not an offspring). It is a stripped-down, dormant form to which the bacterium can reduce itself. Endospore formation is usually triggered by a lack of nutrients, and usually occurs in Gram-positive bacteria. In endospore formation, the bacterium divides within its cell wall, and one side then engulfs the other. Endospores enable bacteria to lie dormant for extended periods, even centuries. There are many reports of spores remaining viable over 10,000 years, and revival of spores millions of years old has been claimed. There is one report of viable spores of '' Bacillus marismortui'' in salt crystals approximately 25 million years old. When the environment becomes more favorable, the endospore can reactivate itself into a vegetative state. Mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sporic Meiosis
Alternation of generations (also known as metagenesis or heterogenesis) is the predominant type of life cycle in plants and algae. In plants both phases are multicellular: the haploid sexual phase – the gametophyte – alternates with a diploid asexual phase – the sporophyte. A mature sporophyte produces haploid spores by meiosis, a process which reduces the number of chromosomes to half, from two sets to one. The resulting haploid spores germinate and grow into multicellular haploid gametophytes. At maturity, a gametophyte produces gametes by mitosis, the normal process of cell division in eukaryotes, which maintains the original number of chromosomes. Two haploid gametes (originating from different organisms of the same species or from the same organism) fuse to produce a diploid zygote, which divides repeatedly by mitosis, developing into a multicellular diploid sporophyte. This cycle, from gametophyte to sporophyte (or equally from sporophyte to gametophyte), is the way ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plant
Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars from carbon dioxide and water, using the green pigment chlorophyll. Exceptions are parasitic plants that have lost the genes for chlorophyll and photosynthesis, and obtain their energy from other plants or fungi. Most plants are multicellular organism, multicellular, except for some green algae. Historically, as in Aristotle's biology, the plant kingdom encompassed all living things that were not animals, and included algae and fungi. Definitions have narrowed since then; current definitions exclude fungi and some of the algae. By the definition used in this article, plants form the clade Viridiplantae (green plants), which consists of the green algae and the embryophytes or land plants (hornworts, liverworts ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alternation Of Generations
Alternation of generations (also known as metagenesis or heterogenesis) is the predominant type of life cycle in plants and algae. In plants both phases are multicellular: the haploid sexual phase – the gametophyte – alternates with a diploid asexual phase – the sporophyte. A mature sporophyte produces haploid spores by meiosis, a process which reduces the number of chromosomes to half, from two sets to one. The resulting haploid spores germinate and grow into multicellular haploid gametophytes. At maturity, a gametophyte produces gametes by mitosis, the normal process of cell division in eukaryotes, which maintains the original number of chromosomes. Two haploid gametes (originating from different organisms of the same species or from the same organism) fuse to produce a diploid zygote, which divides repeatedly by mitosis, developing into a multicellular diploid sporophyte. This cycle, from gametophyte to sporophyte (or equally from sporophyte to gametophyte), is the way ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, such as cyanobacteria, ''Chlorella'', and diatoms, to multicellular macroalgae such as kelp or brown algae which may grow up to in length. Most algae are aquatic organisms and lack many of the distinct cell and tissue types, such as stomata, xylem, and phloem that are found in embryophyte, land plants. The largest and most complex marine algae are called seaweeds. In contrast, the most complex freshwater forms are the Charophyta, a Division (taxonomy), division of green algae which includes, for example, ''Spirogyra'' and stoneworts. Algae that are carried passively by water are plankton, specifically phytoplankton. Algae constitute a Polyphyly, polyphyletic group because they do not include a common ancestor, and although Eu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fungus
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one of the kingdom (biology)#Six kingdoms (1998), traditional eukaryotic kingdoms, along with Animalia, Plantae, and either Protista or Protozoa and Chromista. A characteristic that places fungi in a different kingdom from plants, bacteria, and some protists is chitin in their cell walls. Fungi, like animals, are heterotrophs; they acquire their food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment. Fungi do not photosynthesize. Growth is their means of motility, mobility, except for spores (a few of which are flagellated), which may travel through the air or water. Fungi are the principal decomposers in ecological systems. These and other differences place fungi in a single group of related o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pollen
Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophytes during the process of their movement from the stamens to the pistil of flowering plants, or from the male Conifer cone, cone to the female cone of gymnosperms. If pollen lands on a compatible pistil or female cone, it Germination, germinates, producing a pollen tube that transfers the sperm to the ovule containing the female gametophyte. Individual pollen grains are small enough to require magnification to see detail. The study of pollen is called palynology and is highly useful in paleoecology, paleontology, archaeology, and Forensic science, forensics. Pollen in plants is used for transferring Ploidy#Haploid and monoploid, haploid male genetic ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sporangium
A sporangium (from Late Latin, ; : sporangia) is an enclosure in which spores are formed. It can be composed of a unicellular organism, single cell or can be multicellular organism, multicellular. Virtually all plants, fungus, fungi, and many other groups form sporangia at some point in their biological life cycle, life cycle. Sporangia can produce spores by mitosis, but in land plants and many fungi, sporangia produce genetically distinct haploid spores by meiosis. It's outdated name, sporange, is one of the few perfect rhymes for Orange (colour), orange. Fungi In some phyla of fungi, the sporangium plays a role in asexual reproduction, and may play an indirect role in sexual reproduction. The sporangium forms on the sporangiophore and contains Ploidy, haploid Cell nucleus, nuclei and cytoplasm. Spores are formed in the sporangiophore by encasing each haploid nucleus and cytoplasm in a tough outer membrane. During asexual reproduction, these spores are dispersed via wind and g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seed Plant
A seed plant or spermatophyte (; New Latin ''spermat-'' and Greek ' (phytón), plant), also known as a phanerogam (taxon Phanerogamae) or a phaenogam (taxon Phaenogamae), is any plant that produces seeds. It is a category of embryophyte (i.e. land plant) that includes most of the familiar land plants, including the flowering plants and the gymnosperms, but not ferns, mosses, or algae. The term ''phanerogam'' or ''phanerogamae'' is derived from the Greek (), meaning "visible", in contrast to the term "cryptogam" or " cryptogamae" (, and (), 'to marry'). These terms distinguish those plants with hidden sexual organs (cryptogamae) from those with visible ones (phanerogamae). Description The extant spermatophytes form five divisions, the first four of which are classified as gymnosperms, plants that have unenclosed, "naked seeds": * Cycadophyta, the cycads, a subtropical and tropical group of plants, * Ginkgophyta, which includes a single living species of tree in the genus '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seed
In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds are the product of the ripened ovule, after the embryo sac is fertilization, fertilized by Pollen, sperm from pollen, forming a zygote. The embryo within a seed develops from the zygote and grows within the mother plant to a certain size before growth is halted. The formation of the seed is the defining part of the process of reproduction in seed plants (spermatophytes). Other plants such as ferns, mosses and marchantiophyta, liverworts, do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological Ecological niche, niches on land, from forests to grasslands both in hot and cold climates. In the flowering plants, the ovary ripens into a fruit which contains the seed and serves to disseminate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sporophyte
A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spore, spores. This stage Alternation of generations, alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote produced when a haploid egg cell is fertilized by a haploid sperm and each sporophyte cell therefore has a double set of chromosomes, one set from each parent. All Embryophyta, land plants, and most multicellular algae, have life cycles in which a multicellular diploid sporophyte phase alternates with a multicellular haploid gametophyte phase. In the Spermatophyte, seed plants, the largest groups of which are the gymnosperms (bare seeds) and angiosperms (fruiting plants), the sporophyte phase is more prominent than the gametophyte, and is the familiar green plant with its roots, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gamete
A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878. Gametes of both mating individuals can be the same size and shape, a condition known as isogamy. By contrast, in the majority of species, the gametes are of different sizes, a condition known as anisogamy or heterogamy that applies to humans and other mammals. The human ovum has approximately 100,000 times the volume of a single human sperm cell. The type of gamete an organism produces determines its sex and sets the basis for the sexual roles and sexual selection. In humans and other species that produce two Morphology (biology), morphologically distinct types of gametes, and in which Gonochorism, each individual produces only one type, a femal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
